Answer: b. Water molecules
When sunlight is absorbed by one of many pigments present in photosystem II the light energy is distributed from pigment to pigment until it reaches the reaction center of photosystem II. The electrons present in the reaction center jumps to higher energy state on receiving light energy. Each high energy electron is passed to an acceptor molecule (plastoquinone) and replaced with an electron produced by splitting of water. The splitting of water produces oxygen and electrons. The high energy electrons are transferred to electron transport chain. The energy present in these electrons creates a gradient in the thylakoid membrane of chloroplast. The gradient facilitates the flow of H⁺ ions across thylakoid membrane and which lead to the production of ATP by enzyme ATP synthase.
Therefore, water is required to produce electrons in photosystem II.
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<span>Pollen Grains is also known as male gametophytes of a flowering plant. They represent the male portion in the reproductive process. Pollen grains are tiny bodies which get transported through wind, insect or other natural agents, joins with the female parts of the flower through the process of fertilisation, resulting in the formation of seeds.</span>
I'd try one of these:
*natural selection
*genetic drift
*gene flow
*antigenic drift
<span>Mosses cannot grow tall because they do not have tubes to carry water upwards. They rely on diffusion to carry their water.</span>